DE3033075C2 - Process for the production of high quality carbon binders - Google Patents

Description

The invention relates to a method for producing high quality carbon binders by treating deashed coal at elevated temperature and pressure using of aromatic solvents derived from coal and mineral oil.

Electrothermal refining processes are used in the art to produce a variety of metals used in which carbon electrodes are used. Examples of such refining processes are the manufacture of electrical steel and the Hall-Heroult process for the extraction of technical pure aluminum. For the latter process, carbon is required in large quantities because for Production of 1 t aluminum up to 03 t technical Carbon is consumed (G. Collin, W. Gemmeke, Erdöl und Kohlen, 30,25,1977).

The electrodes used in this case consist of a carbon structure, which is usually made of coke the delayed coking of mineral oil residues or from pitch coke from the coking of coal tar pitch and a suitable one Binder.

Because of its high-quality binding properties, thermally reformed coal tar pitch has mainly been used as a binding agent.

Binders based on mineral oil have not yet achieved the excellent properties of coal tar pitch and are therefore used in industrial applications Only limited application found in practice.

Although the quality assessment for electrode binders is largely empirical (see e.g. E.A. Thomas. Gas World, p. 51, 1960, C. R. Mason, Fuel, 49, 165, 1970) insist on the suitability of a Binding agent certain basic requirements.

According to this, a usable electrode binder must meet the following quality criteria:

A coking residue

(after Conradson)

an ash content

Quinoline-insoluble content Toluene-insoluble content Softening point (K.S.)

> 50%

max. 0.3%

> 7%

> 25% > 80 ° C-120 "C Furthermore, a low sulfur content (< I%), a low metal content and suitable boiling behavior (start of boiling > 270 ° C) is desirable. To avoid the one-sided dependence on Steinkoh tar-based binders in the manufacture of electrodes to abandon the position, there has been no shortage of attempts Increased use of residues derived from mineral oil as binding agent raw materials. Because of the different chemical nature of the

ίο residues from petroleum chemistry compared to However, it is extremely difficult to solve this problem with highly aromatic coal tar pitch: As explained above, the most important property of a good electrode binder is a high coking Residue. Because of the predominantly aliphatic nature of residues derived from mineral oils, it is necessary to achieve this If there are high coking residues, complex thermal or chemical aromatization is necessary. For example, in U.S. Patent 4,039,423, a

M process described after a decanted residue from the catalytic cracking of mineral oil is heated under pressure to temperatures> 413 ° C, the heat-treated pitch to achieve a softening point of 65-121 ^C C of low boiling the constituents is separated and the so obtained Pitch is further thermally reformed by blowing air or oxygen.

In DE-OS 22 32 268 a method is described according to the residues from the steam gap processing of mineral oil fractions into binders will. The disadvantage of this process is that to achieve the necessary highly aromatic Properties an oxidative polymerization and drastic condensation with Lewis acids, in particular re aluminum chloride or ferric chloride is necessary.

In addition to the thermal process steps to be used, these processes have the disadvantage that the yield of binder (based on the feed oil) is <60% and thus there is a large proportion of secondary pro surrendered. In addition, the achievable Coking residues in spite of the complex aromatization only at the lower limit of the desirable qualities. About another attempt to put electrode ties on a base independent of coal tar pitch is prepared by V. L Bullough et al. (Light Metals, pp.483, 1980; CJ. McMinn, Ed; The Metallurgical Society of AIME, Warrendale, P.A., 1979). ·

According to this procedure, a

gene obtained from coal using molecular hydrogen at relatively high pressures Pitch-like product (SRC pitch) fluxed with anthracene oil to set the desired softening point.

Because of the relatively low coking residue of the electrode binder produced in this way the quality of this coal-based binder is also in need of improvement. Since anthracene oil is also preferred for the production of important chemical raw materials for the dye industry, there is therefore only limited availability for these purposes. In addition are a complex filtration or process step upstream of the electrode binder production another thermo-mechanical separation of the Ash constituents for the production of the SRC pitch necessary. This process step represents and is the actual problem stage in coal liquefaction still far from despite various efforts

a technical maturity removed.

The object of the invention was therefore to develop a simple process for the production of high-quality carbon binders and on one of Coal tar pitch largely independent raw material base electrode binder with the known good To produce properties of coal tar pitch,.

According to the invention, this object is achieved by a process for the production of high-quality carbon binders by treating coal with an aromatic solvent in that 5-40 wt .-% mineral oil based aromatic solvents bar an aromatic carbon value material is prepared having an average boiling point above 350 ⁰ C at temperatures of 300-42O ⁰ C and a reaction time of 1-4 hours, under a reaction pressure up to 50, which is freed, where appropriate, low-boiling constituents . ·

By disintegrating in front of ashed coal with a Combination of aromatic solvents from mineral oil processing or petrochemicals and from the Coal processing produces a low-ash, homogeneous carbon material, which is used as an impregnating agent for. B. is suitable for graphite electrodes, and its physico-chemical properties, if necessary highly aromatic additives such as coal tar hard pitch or hard pitch from the processing of Pyrolysis oils, which can be adjusted to be used as electrode binders .. ·

The carbon material obtained in this way may contain up to 5% by weight of low-boiling components Freed by distillation and treated with 0- (Ky Cew .-% hard pitch for the production of the electrode binding jittel mixed homogeneously. As the main raw materials for the production of Electrode binders according to the method according to the invention are used as input materials on which so far The manufacture of high-quality electrode binders cannot be used for reasons of quality could. According to the invention, these are coal and, for the disintegration of the same, residues from the vapor splitting of gasoline or gas oil, residues from Cat crackers, residues from delayed coking and high-boiling aromatic distillates from the Refining of coal tar with a mean boiling point> 350 ° C. For the final setting of the Flow properties, the coking residue and other important quality criteria are according to the invention up to 60% (based on the through *> Disintegration of coal produced coal) distillation residues from the processing of Coal tar pitch or preferably from the distillative work-up of pyrolysis oil with a softening point of 40-160 ° C (K.S.) is used.

The choice of the type of coal is of subordinate importance in the process according to the invention. However, coals with a high carbon content are preferred; the nature of the ashes should be such be that a separation by known methods (z. B. US Pat. No. 4,134,737) is possible. .

However, such ash removal processes are not the subject of the patent application. To the width To ensure that the method according to the invention can be used, a ash removal process was ren selected, after which the ash content of the coal through a particularly intensive chemical treatment with Acids and bases is carried out.

Other ash removal processes that provide ash removal under similar conditions are therefore also suitable for the production of low-ash coals for the process according to the invention.

When using pure coals with an ash content of <1%, the ash separation can even become superfluous.

The ash removal processes for coal generally see drastic chemical reactions Use of acids, bases and oxidizing agents, which have an influence on the carbon dissolution; in particular in the case of oxidative treatment of coal, there is generally a notable deterioration of the dissolving power in aromatics assumed (C. Kroger, Erdöl und Kohlen, 9,1956,441) ..

Surprisingly, however, it has been shown that despite the drastic conditions used in the Ash removal and the associated chemical modification of the coal ensure good homogenization can be obtained with the solvent mixture and thus high quality electrode binder can be produced.

When selecting the solvent components used for coal disintegration, a low ash content is desirable; this requirement is especially in the case of pyrolysis oils from the steam cracking of mineral oil racdones, in the case of distillates from the Coal tar refining and residual oils from delayed coking and also at selected coal tar pitches met residues from catalytic cracking are included low ash content is also suitable as a complementary solvent

However, pyrolysis oils from vapor cracking are preferred in the process according to the invention used by mineral oil fractions, since these oils have a strong tendency to polymerize under the external conditions used in the process according to the invention, which to achieve a high coking residue is advantageous

Distillates from the heat-pressure treatment of coal tar pitch with a medium boiling point are preferred as coal tar oils > 35C ° C or comparable distillates from the distillative processing of coal tar are used.

A simple method of manufacture is thus available of high quality electrode binders are available, especially those that are widely available Raw materials, coal and residues derived from mineral oil can be used as main components.

The production of the binders according to the invention is described in Examples I to 3.

A conventional electrode binder with the well-known good properties is used as a comparison the basis of coal tar pitch was produced (comparative example, example 4).

Mean

Ql: quinoline insolubles TI: toluene insolubles

The softening points were determined by the Krämer-Sarnow method. All quantitative data relate to parts by weight, and all mean the same Percentages by weight.

example 1 Ash removed coal was produced in

Following the US patent 41 34 737, Thereafter, I part by weight of finely divided Westerholt gas flame coal (ash content 7.8%, volatile content waf 3i, j%) with 4 parts by weight of IO% sodium hydroxide at 250 ⁰ C for 3 hours Treated

The washed reaction product is further treated with 2 parts by weight dilute sulfuric acid (5%) at 80 ⁰ C and a reaction time of 30 minutes.

The final treatment is with 1.5 parts by weight of 18% nitric acid at 75 ° C. and for a duration of reaction carried out for 1 hour

The ash content of the coal treated according to these 3 different process steps amounts to 03% - The yield corresponds to the theoretical one Calculation (93.1%).

To produce electrode binders, a reaction mixture is made from

30 parts by weight of ashed Westerholt coal,
30 parts by weight of pyrolysis residue from steam-cracking of petrol (boiling point 220 ⁰ C. 50% at 360 ° C) and

40 parts by weight of pitch distillate from the heat-pressure treatment of coal tar pitch (initial boiling point 305 ⁰ C, 50% at 416 ° C, 80% at 455 ° C)

at 375 ° C and a reaction time of 2 hours homogenized well mixing. The maximum reaction pressure is 24 bar. One receives after the separation of 3% low-boiling components in 95% yield a pitch-like coal resource, the one with 30% hard pitch from the processing of coal tar pitch normal pitch (production see US Pat. No. 2,985,577) is mixed homogeneously. The softening point of this hard pitch is 160 ° C (K.S.). The binder produced in this way is characterized by the data given in the table.

Example 2

30 parts by weight of ashed Westerholt gas flame coal are with

20 parts by weight of pitch distillate from the heat-pressure treatment of coal tar pitch,

40 parts by weight of pyrolysis residue from the cleavage of gasoline, as described in Example 1 and

10 parts by weight of cat cracker residues

treated at 400 ° C and 3 hours reaction time. Of the maximum reaction pressure is 40 bar.

After 3% of low-boiling constituents have been separated off, the reaction product obtained is a carbon material with a softening point of 60 ^° C. (KS) in 95% yield. This coal value is mixed homogeneously with 50 parts by weight of hard pitch, which comes from the distillation of pyrolysis residues that arise during the cleavage of raw gasoline. The softening point of this hard pitch is 135 ° C (KS).

The binder produced in this way is characterized by the data given in the table

Example 3

Proceed as in example 1.

The coal used is a gas cabbage with a volatile content of 26.5% and an ash content of 13% are used. Ash removal is carried out as in Example 1 described; the residual ash content of the Kon! «is 0.8%.

30 parts by weight of ashed gas fired coal are mixed with 40 parts by weight of pitch distillate from the heat-pressure treatment of coal tar pitch and 30 parts by weight of pyrolysis oil from the steam cracking of raw gasoline

implemented at 400 ⁰ C and a reaction time of 2 hours with thorough mixing. The maximum reaction pressure is 18 bar.

Is obtained in 97% yield IGCR a pitch-like carbon valuable substance having a softening point of 80 ⁰ C (KS). This carbon material is separated from low boilers (3%) and 30% hard pitch with a softening point of 135 ° C (KS) from the detillative

Processing of pyrolysis oil mixed homogeneously

The binder produced in this way is characterized by the data given in the table.

Example 4 (comparative example)

For comparison, the table shows a conventional one Electrode binder on the basis of coal tar pitch listed.

Tabel Characterization of the electrode binders

Raw material components

Product features

Coking softening ash content QI TI

backlog point

(after (K. S.)

Conradson) ⁰ C%%%

Example 1: carbon material from

30 parts by weight of Westerholt coal 51

30 parts by weight of pyrolysis residue

40 parts by weight of pitch distillate and

30 parts by weight of hard pitch

Example 2: carbon material from

30 parts by weight of Westerholt coal 54

20 parts by weight pitch distillate

40 parts by weight of pyrolysis residue

10 parts by weight cat cracker and

50 parts by weight hard pitch

90

93

0.28

0.29

13th

10

38

32

continuation

KiihsliillVimipiincnlrn

V'crkokungs- tirwcithuiiys- Whegehnll 'Jl

residue punkl

(after (KSi

Conradson) ⁰ C "■ ·

Example 3: Coal valuable from 30 parts by weight of oasc coal 40 parts by weight pitch distillate

30 parts by weight of pyrolysis oil and 30 parts by weight of hard pitch

Example 4: (comparative example) conventional electrode binder from coal tar pitch

clarification: Ql - (Jhinoninsoluble TI = toluene insolubles

0.26 0.27

14.5

13th

Claims (2)

Patent claims: 1. Process for the production of high-quality carbon binders by treating coal with an aromatic solvent, characterized in that 5-40% by weight of deashed coal is treated with 20-80% by weight of coal-based and 15-50% by weight of aromatic solvents based on mineral oil bar an aromatic carbon value of the material is freed, where appropriate, of low-boiling ingredients is prepared having an average boiling point above 350 ⁰ C, at temperatures of 300-420 ⁰ C and a reaction time of 1-4 hours, under a reaction pressure up to 50. 2. Use of the carbon binder obtained according to the preceding claim, optionally in a mixture of up to 60% by weight Mineral oil or coal-based hard pitch as an electrode binder.